1. Field of the Invention
The present invention relates to a high pressure gas seal between a high speed rotating shaft and a stationary housing. More particularly, the invention is directed to a seal which utilizes nozzles and vanes to produce a gas seal between the shaft and housing.
2. Description of the Prior Art
Seals between a shaft and housing typically have touching parts to seal in the static condition and then means to separate when the shaft is rotating, thereby allowing some leakage and reducing wear. The force balance between the seal and seal plate is usually accomplished by grooves, pads, and similar structures which are balanced against springs during static conditions and lift the seal from the seal plate for dynamic operations. Several problems exist with these types of seals. There is always some wear when the shaft begins rotating until the opposing elements of the seal lift off. Further, the springs are always in motion due to axial end play of the shaft and fatigue fail with time. In addition, there may be oil present from nearby bearings that vaporizes and burns on the seal plate which highly affects the coefficient of friction between the sealing face and the seal plate.
The prior art seals known to the applicant present significant problems when the speed of the shaft is high, often over 10,000 rpm. The high rpm of the shaft gives rise to very high rotating stresses in the seal plate itself. The seal plate must be appropriately balanced and sized such that stress concentrations are kept to a minimum. The seal plate itself in high speed seals is typically a mass of steel one to two inches thick with a central hole and grooves to drive it at the rpm of the shaft. This seal plate is usually ground and polished and must be balanced very acutely to minimize the rotating stresses. Any error in balancing the seal will adversely affect the stability of the seal. Similarly, the seal is subjected to variations in temperature and pressure which adversely affect the stability of the seal plate.